<template>
  <div>
    <input id="excel-upload-input" ref="excel-upload-input" type="file" accept=".xlsx, .xls" @change="handleClick">
    <el-button class="select-btn" :loading="loading" size="medium" type="primary" @click="handleUpload">批量上传</el-button>
    <!--<div id="drop" @drop="handleDrop" @dragover="handleDragover" @dragenter="handleDragover">
      <div class="drop-content">
        将文件拖到此处，或点击 <span class="text-primary">选择文件</span> 按钮
        <br>
      </div>
      <div class="mt20"><slot></slot></div>
    </div>-->
  </div>
</template>

<script>
  import XLSX from 'xlsx'

  export default {
    name: 'UploadExcel',
    props: {
      headerKeys: {
        type: Array
      },
      beforeUpload: Function,
      onSuccess: Function
    },
    data() {
      return {
        loading: false,
        excelData: {
          header: null,
          results: null
        }
      }
    },
    methods: {
      generateDate({ header, results }) {
        this.excelData.header = header
        this.excelData.results = results
        this.onSuccess && this.onSuccess(this.excelData)
      },
      handleDrop(e) {
        e.stopPropagation()
        e.preventDefault()
        if (this.loading) return
        const files = e.dataTransfer.files
        if (files.length !== 1) {
          this.$message.error('一次只能上传一个文件!')
          return
        }
        const rawFile = files[0] // only use files[0]

        if (!this.isExcel(rawFile)) {
          this.$message.error('只能选择 .xlsx, .xls, .csv 文件！')
          return false
        }
        this.upload(rawFile)
        e.stopPropagation()
        e.preventDefault()
      },
      handleDragover(e) {
        e.stopPropagation()
        e.preventDefault()
        e.dataTransfer.dropEffect = 'copy'
      },
      handleUpload() {
        document.getElementById('excel-upload-input').click()
      },
      handleClick(e) {
        const files = e.target.files
        const rawFile = files[0] // only use files[0]
        if (!rawFile) return
        this.upload(rawFile)
      },
      upload(rawFile) {
        this.$refs['excel-upload-input'].value = null // fix can't select the same excel

        if (!this.beforeUpload) {
          this.readerData(rawFile)
          return
        }
        const before = this.beforeUpload(rawFile)
        if (before) {
          this.readerData(rawFile)
        }
      },
      readerData(rawFile) {
        this.loading = true
        return new Promise((resolve, reject) => {
          const reader = new FileReader()
          reader.onload = e => {
            const data = e.target.result
            const fixedData = this.fixdata(data)
            const workbook = XLSX.read(btoa(fixedData), { type: 'base64' })
            const firstSheetName = workbook.SheetNames[0]
            const worksheet = workbook.Sheets[firstSheetName]
            const header = this.get_header_row(worksheet)
            const results = XLSX.utils.sheet_to_json(worksheet)
            this.generateDate({ header, results })
            this.loading = false
            resolve()
          }
          reader.readAsArrayBuffer(rawFile)
        })
      },
      fixdata(data) {
        let o = ''
        let l = 0
        const w = 10240
        for (; l < data.byteLength / w; ++l) o += String.fromCharCode.apply(null, new Uint8Array(data.slice(l * w, l * w + w)))
        o += String.fromCharCode.apply(null, new Uint8Array(data.slice(l * w)))
        return o
      },
      get_header_row(sheet) {
        const headers = []
        const range = XLSX.utils.decode_range(sheet['!ref'])
        let C
        const R = range.s.r /* start in the first row */
        for (C = range.s.c; C <= range.e.c; ++C) { /* walk every column in the range */
          var cell = sheet[XLSX.utils.encode_cell({ c: C, r: R })] /* find the cell in the first row */
          var hdr = 'UNKNOWN ' + C // <-- replace with your desired default
          if (cell && cell.t) hdr = XLSX.utils.format_cell(cell)
          headers.push(hdr)
        }
        return headers
      },
      isExcel(file) {
        return /\.(xlsx|xls|csv)$/.test(file.name)
      },
      /**
       * @arguments headerKeys header 对应的 key
       * @return []
       */
      // excelData to json
      getJSON() {
        let keysMaps = {}
        let data = this.excelData
        let headerKeys = this.headerKeys
        console.log(data, headerKeys)
        _.each(data.header, (name, index) => {
          keysMaps[name] = headerKeys[index]
        })
        return _.map(data.results, row => {
          let item = {}
          _.forOwn(row, (val, key) => {
            item[keysMaps[key]] = val
          })
          return item
        })
      }
    }
  }
</script>

<style lang="less" scoped>
  #excel-upload-input{
    display: none;
    z-index: -9999;
  }
  #drop{
    border: 2px dashed #ccc;
    width: 500px;
    padding:80px 40px;
    margin: 0 auto;
    border-radius: 5px;
    position: relative;
    .drop-content{
      font-size: 18px;
      text-align: center;
      color: #bbb;
    }
    .select-btn{
      font-size:20px;
      padding:15px 80px;
      margin-top: 50px;
    }
  }
</style>
